Haven't we heard this story before? Yes. We've been round this block many times. And many times Armstrong and his people have denied the allegations, pointed to his record of never having tested positive, cast aspersions on the bona fides of those making the accusations, and taken legal action if necessary.

He is the seven-time winner of the Tour de France, not a dope cheat, and it would be unwise to suggest otherwise.

That is certainly the view of Lance Armstrong that pertains among the vast majority of the American public, and internationally, too. To these millions, Lance Armstrong is the inspirational cancer survivor who came back virtually from the dead and claimed the cycling world's most coveted title an astonishing seven consecutive times. He is an all-American hero, who has used his fame to raise millions for fighting cancer. He has become a brand that's far bigger than professional bike racing. How many people who've worn a yellow Livestrong wristband do you suppose have even heard of Tyler Hamilton or Floyd Landis, who, unlike Lance, have been busted for doping and are now hawking to publishers their tawdry tales of pills and syringes in the peloton?

But there is now a big difference, potentially. Tyler Hamilton's allegations on CBS over the weekend are, he would have us believe, the same testimony he has given under oath to the federal investigation's grand jury, which will decide whether there is sufficient evidence to launch a prosecution of Armstrong and his associates on the US Postal team for fraud – that is, taking federal funding under false pretences (by being sponsored to race and win clean, when, in fact, they were using performance-enhancing drugs). More credible than Hamilton, George Hincapie, another long-time team-mate of Armstrong's, is also reported to have testified before the grand jury that the team was doping. Armstrong's lawyer has issued denials of these new allegations.

The game-changer here is that the justice department and FBI have the powerful weapon of subpoenaing witnesses and compelling them to testify under oath. Few former professional racing cyclists, recently retired, with young families, a little anxious about their investment portfolios and thinking about what to do next after 15 years in the saddle, are going to be willing to risk a charge of perjury out of loyalty to associates in a sport they're no longer in.

There is a larger question raised by this latest episode, which has involved an allegation – strongly denied by the parties accused – that cycling's governing body, the UCI, was involved in a backroom deal in 2001 between Armstrong, his manager and a Swiss laboratory to suppress a positive test for the blood-doping agent EPO. And that question is: given the persistence of cycling's apparent issue with doping, is its governing body sufficiently independent and possessed of the political will to police the problem? All the really big systemic busts in cycling have been not by anti-doping authorities, but by old-fashioned police work: the Festina scandal in 1998, the Operación Puerto investigation of 2006-2007, and now – maybe – the feds in the US.